Unaccustomed Eccentric Contractions Impair Plasma K+ Regulation in the Absence of Changes in Muscle Na+, K+- ATPase Content

作者：Goodman Craig A; Bennie Jason A; Leikis Murray J; McKenna Michael J^*

来源：PLos One, 2014, 9(6): e101039.

DOI：10.1371/journal.pone.0101039

The Na+, K+-ATPase (NKA) plays a fundamental role in the regulation of skeletal muscle membrane Na+ and K+ gradients, excitability and fatigue during repeated intense contractions. Many studies have investigated the effects of acute concentric exercise on K+ regulation and skeletal muscle NKA, but almost nothing is known about the effects of repeated eccentric contractions. We therefore investigated the effects of unaccustomed maximal eccentric knee extensor contractions on K+ regulation during exercise, peak knee extensor muscle torque, and vastus lateralis muscle NKA content and 3-O-MFPase activity. Torque measurements, muscle biopsies, and venous blood samples were taken before, during and up to 7 days following the contractions in six healthy adults. Eccentric contractions reduced peak isometric muscle torque immediately post-exercise by 26 +/- 11% and serum creatine kinase concentration peaked 24 h post-exercise at 339 +/- 90 IU/L. During eccentric contractions, plasma [K+] rose during Set 1 and remained elevated at similar to 4.9 mM during sets 4-10; this was despite a decline in work output by Set 4, which fell by 18.9% at set 10. The rise in plasma [K+].work(-1) ratio was elevated over Set 2 from Set 4- Set 10. Eccentric contractions had no effect on muscle NKA content or maximal in-vitro 3-O-MFPase activity immediately post- or up to 7 d post-exercise. The sustained elevation in plasma [K+] despite a decrease in work performed by the knee extensor muscles suggests an impairment in K+ regulation during maximal eccentric contractions, possibly due to increased plasma membrane permeability or to excitation-contraction uncoupling.

• 出版日期2014-6-24